TypeScript的函数重载 | 青训营笔记

函数的类型

//注意，参数不能多传，也不能少传 必须按照约定的类型来
const fn = (name: string, age:number): string => {
    return name + age
}
fn('张三',18)

函数的可选参数

//通过?表示该参数为可选参数
const fn = (name: string, age?:number): string => {
    return name + age
}
fn('张三')

函数参数的默认值

const fn = (name: string = "我是默认值"): string => {
    return name
}
fn()

接口定义函数

//定义参数 num 和 num2  ：后面定义返回值的类型
interface Add {
    (num:  number, num2: number): number
}
 
const fn: Add = (num: number, num2: number): number => {
    return num + num2
}
fn(5, 5)
 
 
interface User{
    name: string;
    age: number;
}
function getUserInfo(user: User): User {
  return user
}

函数重载

let yioo: number[] = [1, 2, 3, 4]
function findNum(add: number[]): number[]
function findNum(id: number): number[]
function findNum():number[]



function findNum(ids?: number | number[]) {
  if (Array.isArray(ids)) {
    yioo.push(...ids);
    return yioo
  }
  else if (typeof ids == 'number') {
    return yioo.filter(y => y == ids)
  }
  else {
    return yioo
  }
}

console.log(findNum());
console.log(findNum(1));
console.log(findNum([5,6,7]));